Thermostatic safety control for burners



Sept. 9, 1952 A. CLARKSON 2,609,867

THERMOSTATIO SAFETY CONTROL FOR BURNERS Original Filed April 28, 1948 2 SHEETS--SHEET l df. l @l j@ IN VEN TOR.

-2 'SHEETS- SHEET 2 A. CLARKSON INVENToR.

THERMOSTATIC SAFETY CONTROL FOR BURNERS NEVE WKN Sept. 9, 1952 Original Filed April 28, 1948 mm. I. l5 u\ u` Patented Sept. 9, 1952 UNITED STATES, PATNT-- QFFICE?,

rnERMos'rA'rio SAFETY CONTROL- ron BURNERS rAlick Clarkson, Itasca, Ill., assigner of one-halt to Vapor Heating Corporation, Chicago, Ill., a y corporation of Delaware i Original application April 28, 1948,- SerialA No.

23,728. Divided and this application Febrar 10, 1950, Serial No. 143,529 i claims. (o1. 15s- 28) One ofthe objects of my invention is the provision of a safety control of high sensitivity which is immediately responsive to temperature variations directly within the combustion chamberof ra heat generator to insure prompt stoppage ci the flow of fuel in the event o'f accidenta-lextinguishment of the nre.

The important function of the structure of the present rinvention is to shut on the delivery of fuel and combustion air tov the combustion chamber of a gas or oil :nredheat generator in the event that the name isf extinguished fortuit'ously and not immediately re-.established. In order. to provide high/sensitivity and thereby insure prompt stoppage of the delivery of fuel, the invention includes the provision of means whereby a thermostatis subjected tov heat directly fromV the `combustion chamber. However, a thermostat suitable fortl-iisjob and sufficiently sensitive to afford quick action is apt to befdamage'd if subjected to a peak combustion chamber temperature. Itis therefore an important object of the present invention to provide certain improved arrangements wherebyV a highly'` sensitive thermostat may be used in a vcor'itro'l mechanism adapted to respond to a maximum volume of hot gases directly from the combustion chamber, so` as to provide immediate responses to temperature conditions within the combustion chamber, but is protected from' thedestruc'tive effects of high temperatures.

According to the present invention a conduit connection leads from the combustion chamber of a heatv generator toV a suction device, preferably the suction side of a blower utilized to deliver combustion' air to the combustion chamber. The blower, therefore, in' addition to delivering' combustion air' to the combustion chamber withdrawsa small volume of hot gases therefrom.r These not" gases are intermix'ed with a quantityr of air, at room temperatures, and the gaseous mixture, so reduced temperature, is passedlinto contact with a thermostat which is housed within said conduit. The volume rof hot gases withdrawn from the combustion chamber is proportionately reduced as the temperature o f the nre chamber increases, but the volume of cool air mixed with the hot gases remains substantlally constant. The above result is obtained by means of a valve which is operatively connected with the thermostat so as to be moved into a position to Vprogressively obstruct the admissionof hot gases into the thermostat cham- `ber as kthe temperature of these gases increase.

Other rand further objects and advantages of my invention will become apparent from the following description when considered in connection with the accompanying drawings in which: A

Fig. 1 vis a front elevational view oi a horizontal boiler and associated oil burner unit, and illustrating my invention applied thereto.

Fig. 2 is a fragmentary plan view of the structureillustrated in Fig. 1.

Figiiis a longitudinal cross-sectional view of a structure in accordance with my invention, taken on line 3 3 of Fig. 4.

Fig.- 4 is a view of one end of the structure showing the thermostatically actuated switch mechanism.

. Fig.` 5 is a view of the other end of the structure looking? in the direction of the arrows 5-5 of Figi Fig. 6 is a' cross-sectional View taken on line 6'-- Ii` of Figi 3.

lReferring' to the drawings, my invention is shown by of illustration as applied to a water' heater utilizing oil as a fuel. It will be understood, however, that my invention is capable' of application to other types of heat gencratersV employing liquid or gaseous fuels as a heating nfle'dia. The heat generating unit illustrated comprises a boiler, indicated generally by thenuineral I', the said boiler being of any suitable construction and havingv a combustion chamber', .and aburner unit indicated generally at L l, the said una including a nozzle assembly I2', a spiral nduit I3, a blower I4 driven by an electrical notor' I6 for delivering air into the combustion chanter through said Conduit la', and fuel pump I'I driven by the same motor,- the said fuel pump being connected` to the nozale assembly I2 by a conduit I8.

The control means constituting my invention is indicated generally by the numeral I9 an'disshown Figs. 1 and 2 in relation to the other c om1 n one11tsV ofthe heat generating unit and is illustrated inrdetail in Figs. 3 to 6, inclusive. Ihe said control means includes a'tubular housingZI to which is connected, at one'end' thereof,

becomes extinguished while-the blower v|4 is inY operation, the temperature of the gases passing through the housing 2| will immediately drop, Y and conversely, should the fire become reestab- The blower |4, in addition to supplyingV (through suitable relays not shown) the circuit of motor |6 which drives the blower I4 and fuel pump I1, the object being to automatically stop the operation of the blower and fuel pump whenever the fire in the heating unit may be extinguished fortuitously; and -to jhold the motor circuit closed so long as the fire is on. The switch 39 referred to is illustrated in Figs. 3 and 4 and ported by boltsl 42 which pass through apertures in the panel 4| and through the back wall of the lished, the temperature of the gases passing through the housing will immediately rise.

Mounted on one end of the tubular housing 2| is a cap 21 arranged to support a bushing 28 in which is -journaled a 'shaft 29. The cap 2-1 is provided with a plurality of perforations 3| through which a substantially constant volume of air from the surrounding space may be admitted into the interior of the housing 2|.` Received in the opposite end of the housing 2| is a flanged member 32 having an integral elongated tubular pody Aportion 33 concentric with the wall-of the housing 2 I The'said tubular portion 33 supports a bushing 34 which serves as a journal for the opposite Yend of the shaft 29. The manifold is provided with a flange 24a against which is abutted a mounting plate 25, the said flange and plate having registering perforations to receivescrews for mounting a switch 39, hereinafter to be described. As seen in Fig. 3, the shaft 29 projects to the left, beyond the housing 3| and is operatively connected to the mechanism of switch'30, as will be hereinafter described.` l

Mounted on the shaft 29 for rotation therewith and disposed in alignment with the intake opening 35 of housing2| is a semi-cylindrical damper valve 36. The curvature of the damper 36 is concentric with the wallY of the housing 2| and is spaced therefrom so as to provide a substantial clearance between the outer surface of the damper 36 and the inner surface of the tubular housing 2|. Hence, even though the damper36 is rin fully closed position, a reduced volume of hot gases may be drawn through the intake opening 35 into the housing 2|. In Fig.'6the damper 36 is shown in its fully opened position, and as will be apparent by reference to this figure, counterclockwise rotation of the damper 36 progressively reduces the volumeof hot gases and that movement thereof through an angle of approximately 90 degrees will bring it to its fully closed position.

A thermostat element 31 comprising a bimetallic ribbon in the form of an elongated helix is arranged concentric to the shaft 29 and is fixe'dly secured at one end to the tubular portion 33 and at the other end to a sleeve-like extension 38 o f the damper` 36. The damper 36 is fixed to the shaft 29 through the medium of a pin 39 which extends diametrically through registering openings'in the damper and shaft. Thus, the damper 36 and shaft 29 are caused to rotate as a unit when actuated by the thermostat 31 which operates, in a well known manner, t produce a torsional or twisting movement in response to temperature changes. rlhis twisting movement imparts corresponding rotational movement to shaft 29 and damper 36. r

,One of the functions of shaft 29 isftooperate the mechanism of a switch 130 for controllingl housing 38. The said bolts pass through spacers v 43 and through apertures in the plate 25 and flange 24a and are secured by means of nuts 44 and 45. Pivotally supported on a pin 46 carried on the panel 4| is a metal plate 41 which may be locked in a position of adjustment by a bolt 48 passing through an arcuate slot provided in the panel 4|. -A metal block 49 which may beintegral with plate 41- is slotted to'receive and `secure therein one end of the contact spring 5| which carriers at its free end a contact 52 adapted to engage a fixed contact 53. The said contact is mounted on a metal plate 54 which is pivotally supported-on a pin 56, the said plate being locked vin a position of adjustment by a bolt 51 which passes through an arcuate slotY in the panel 4|. Thus, by reason of the pivotal supports of the plates 41 and 54, relative adjustment between the contacts 52 and 53 may be effected.

Mounted on shaft 29 and fixed thereto, as with a pin 58., is a collar 59. The collar 59 has a centrally recessed portion 6| lto provide an annular face 52. Mounted ony shaft 29, but not fixed thereon, is a cam indicated generally by numeral 63, the said cam being provided with a rounded nose portion 64 and being notched on its rearward end, as at 6'6, to accommodate therein a stop pin 61, and stop pin being anchored 'in the panel4l. It will be apparent that the presence of the p in'61 in the notch 6.6 limits rotationalcmovement of the pin 63, in either direction, to a very small angle. Cam 63 is maintained in frictional abutment vwith the annular face `6i? of l.the sleeve 59' by Aa spring 58, which is interposed between, a pair of dished metal discs 19 `and11| bearing against the side face of the cam 63jand aA retaining pin-12 respectively, the said pin being driven through shaft 29. It'will be evident that "the mechanism herein described operatesv as a frictional clutch to impart rotation of the shaftk 29 to the cam' 63, this rotation continuing until the cam 63 is moved into engagement with stop pin'61.V l

The operation of mycontrolmeans will now ,be described. When no fire is on and the thermostat element31 is subjected to the ambient temperature `of the atmosphere, damper36 .isin its fullt-7 openedposition, substantially as shown 'in Fig.` 6l However, almost instantaneously upon 4the introduction of nre lin thecombustion chamber of thehe'at .generating unit, ablast of'hot'gasesisV drawn into'the housing 2|, andthe thermostat element 31 will respond to the change in temperature and will effect rotation.ofshaft29 to move the' damper36 in a c ounterclockwise direction, as viewedinlig. 6, toward its Vclosed position.' As they damper. 36 moves' toward closed position, it progressively restrictsl the intake opening 35, thereby correspondingly.reducing the. volume of hotgases being admittediintothe housing 2|. During lthe Tmovement,v VOf'hot gases" through the housing v2 cooling air' in substantially, 'constant volume is vdrawn from the ambient space through accasev .5 the apertures 3| and intermixesfwith theqhot gases of Vcombustionto lower the temperature thereof within thehousing'Zl.. .As the tempera- `ture vof the gases of. combustion increaseathe damper r3&5 will move progressively fartherin a direction to close the intake-opening toxproportionately restrict'the admission of .hot gases into. the housing 2|, thus tending to maintain a constant, but desirable low temperature within the housing 2li, so as not to subject the thermostat element 31 to, excessively high ordamaging temperatures, aslong as the nre keeps going.

. The arrangement above described permits the use of a highly sensitive thermostat, and vnot only insures against injury tothe thermostat element, but also affords almost immediate response to temperature changeaas to/both starting and extinguishing of the fire. Upon starting of the fire, the thermostat 31 is subjected at once to: a

full blast of heat because the damper 36is in its f open position and the intake .opening 35 is completely unrestricted. When the re is extinguished from some reason, the thermostat 3.' is quickly effective to rotate the shaft 29 to actuate the swtich to open the motorcontrol .circuit and thereby to stop the motor driving the blower and fuel pump. This is accomplished because. the thermostat 37 is thenzsubjected toaare1atively cooler stream of air that is drawn into the housing 2| through apertures-l.

As will be apparent by reference to Fig. 3, when the shaft 25 is caused to rotate, in onev direction or another, as hereinbefore described, the cam -willmove correspondingly 1with the shaft. However, its movement is limited by thepin 61 which permits the cam 63 to move just a few degrees in eitherA direction. Thus, even though the shaft 29 continues moving, the cam remains stationary after it contacts the stop pin 61. When the cani is rotated in a counterclockwise direction, as seen in Fig. 4, it deflects spring 5l in a direction to bring about the disengagement of contacts 52 and 53, and when rotated a few degrees in a clockwise direction from the open contact position, the ccntacts 52 and 53 are urged into engagement, as in the position shown in Fig. 4. It will be seen that a very small angular displacement of cam 53, in either direction is effective to make or lorca-kcontact, depending upon the direction of rotationof the cam 63. As a result of this 'construction a small increase in temperature within the housing 2l will effect a contact operation of one kind, while a similarly small decrease in temperature will effect a contact operation of the opposite kind, irrespective of how high the temperature within the combustion chamber may b-e when the change begins to take place. It will be evident therefore, that even though the shaft 29 may have rotated 80 degrees or more, incidental to damper 36, from its fully opened to fully closed position, nevertheless, a very slight rotation of shaft 29 in the opposite direction will rotate the cam B3 sufficiently to actuate the switch contacts 52 and 53. Similarly, a very slight rotation of shaft 29 in the opposite direction will effect an actuation of switch contacts 52 and 53 of the opposite character.

In the particular case illustrated, contacts 52 and 53 are caused to open relative to each other in response to a decrease in temperature in the housing 2l. It will be understood however that other control circuit arrangements may be adopted in which, for example, contacts 52 and 53 are caused to open in response to a temperature increase. Since the invention is not concerned Withthe motor control circuit, the circuitisnot shown'in the drawings and is not here considered.

Manifestly there are numerous possible modifications and alternatives vwithin the scope of the inventive concept herein disclosed, and accordingly, the'invention is not tobe limited otherwise than as indicated by the terms of the appended claims.

l. An automatic outfire control device comprising a conduit having a lateral intake p'ort near. oneend and adapted to be connected with thecombustion chamber of a furnace, the other end of saidconduit being adapted to be connected to the' intake side of a blower, whereby hot gases-may be Withdrawn from such furnace into said conduit, a bimetallic thermo-responsive elongatey helical element disposed within said conduit and co-axial therewith,`one end of said element being xedly anchored against rotation yrelatively t0 said conduit,A a shaft extending axially through said element and connectedto the other end thereof forV rotation therewith. a damper carried by said shaft and having a curved surface arranged concentric with the inner surfaceV of said conduit for movement across said intake port to variably constrict the same as `the .temperature of said thermo-responsive ele.-

ment increases, said curved surface of the damper being of smalle'rradius Vthan that of the bore of said conduit soV that when the damper is in fully closed posture it is still slightly open, thus insuring that some hot gas will flow through said conduit even'when'the damper is closed, and an air-intake port. leading into said conduit for admitting air from the ambient atmosphere, said air-intake port being located adjacent the .unanchored end of said thermo-responsive element so that the air. entering the conduit therethrough traversessaid kelement to prevent overheating thereof. 4

12..An automatic outre control device comprising aconduit having an intake port adjacent one end. adapted to be vconnected with the cornbustion chamber of a furnace, the other end of said conduit being adapted to be connectedv to the intake side of a blower, whereby hot gases may be withdrawn from such. furnace into said conduit, a bi-metallic.thermo-responsive elongated helical elernent disposed within said conduit and co-axial therewith, one end of said element being fixedly anchored against rotation relatively to said conduit, a shaft extending axially through said element and operatively connected with the other end thereof so as to be rotatable thereby, an electric switch operatively connected with said shaft, a damper carried by said shaft and rotatable therewith, said damper being disposed within said conduit and adjacent said intake port and operative upon rotation to variably constrict said port, the arrangement being such that said damper increasingly constricts said port as the temperature of said element increases, said damper being spaced away from said port so that the port remains slightly open when the damper is in its fully closed posture, and an air-intake port leading into said conduit for admitting air from the ambient atmosphere, said air-intake port being located adjacent the unanchored end of the thermo-responsive element so that the air entering the conduit therethrough traverses said element to reduce the heating effect of said hot gases thereon.

3. An automatic outre control device comprising a conduit having an intake port adjacent one end adapted to be connected with the combustion chamber of a furnace, the other end of said conduit being adapted to be connected to the intake of a blower, whereby hot gases may be withdrawn from such furnace into the conduit, a bi-metallic thermo-responsive elongated helical element disposed within said conduit and co-axial therewith, one end of said element being fxedly anchored against rotation relatively to said conduit, a shaft extending axially through said .element and operatively connected to the unanchored end thereof so as to be rotatable thereby, a switch actuating member carried on said shaft, means associated with said shaft for frictionally driving said actuating member, a damper carried by said shaft and rotatable therewith, Ysaid damper being disposed within said conduit and adjacent said intake port and operatve upon rotation to variably constrict said port, the arrangement being such that said damper increasingly constricts said port as Athe temperature of said element increases, said ldamper being spaced away from said port so that `the port remains slightly open when the damper `is in its fully closed posture, and an air-intake port leading into said conduit for admitting air .from the ambient atmosphere, said air-intake port being located adjacent the unanchored end of said thermo-responsive element so that the :air entering the conduit therethrough traverses said element to reduce the heating effectY of said hot gases thereon.

4. In combination with means defining a combustion chamber and means including a fuel pump and a blower for delivering fuel and air .into the combustion chamber, of an automatic outiire control comprising a thermo-responsive element having a portion movable in response to .temperature changes, a conduit surrounding said thermo-responsive element and having anintake port near one end connected with the combustion chamber, the other end of the conduit being connected to the suction side of said blower, whereby hot gases are withdrawn from the combustion chamber and brought into contact with said thermo-responsive element, a damper located within said conduit adjacent said intake port and operatively connected with said 'movable portion of said thermo-responsive element,

whereby movement of thedamper progressively constrictssaid port as the temperature of the thermo-responsive element increases, and an air intake port leading into said conduit adjacent to the movable portion of the thermo-responsive element to admit air into the conduit and thereby reduce the temperature of the hot gases therein.

5. In combination with means defining a combustion chamber and means including an electrically energized motorand a fuel pump and a blower operated thereby to deliver fuel and air into the combustion chamber, of an automatic outfre control comprising a thermo-responsive element having a portion movable in response to temperature changes, a conduit surrounding said element and having an intake port near one end connected with the combustion chamber, the other end of the conduit being connected to the suction side of said blower, whereby hot gases are withdrawn from the combustion chamber and brought into contact with said thermoresponsive element, a shaft operatively connected with the movable portion of said thermoresponsive element, a damper located within the conduit and operatively connected with said shaft for movement across said port to partially constrict the same and thereby reduce .the volume of hot gases drawn into the conduit, a switch actuating member carried on said shaft, means associated with said shaft for frictionally driving said actuating member, and an air-intake port leading into the conduit adjacent the movable portion of said thermo-responsive element, so as to admit air into the conduit to reduce the temperature of the hot gases therein.

ALICK CLARKSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Re. 16,444 Fesler Oct. 26, 1926 1,640,728 Scott Aug. 30, 1927 1,663,442 Culp Mar. 20, 1928 1,664,339 Williams Mar. 27, 1928 1,782,937 Perry Nov. 25, 1930 2,325,964 Macchi Aug. 3, 1943 

